PLANT FORM AND FUNCTION

1. PLANT FORM AND FUNCTION UNIT SIX Chapters 35,36,37,38,39

2. Angiosperm Structure • Angiosperms are further divided into 4 major categories: • Basal Angiosperms (older angiosperms like Water lilies) • Magnoliids (newer like the Magnolia) • Monocotyledons a.k.a. monocots (newer still) Have a single seed leaf - Dicotyledons and/or Eudicotyledons a.k.a. eudicots (newest) Have double seed leaves

3. Palms and Bananas are Monocots Rice, wheat, corn – all monocots

4. Monocots vs. Dicots

6. Basic Angiosperm Morphology • Shoot system= stems and leaves • Root system= tap root and lateral roots

7. Plant Morphology • Stems consist of alternating “nodes”, the site of leaf attachment • The angle created where the leaf attaches to the stem is called the axil • The axil contains an axillary bud, which can give rise to a lateral shoot or a branch • The tip of the shoot is called the apex and holds the terminal bud • The terminal bud and the apex is where the elongation of the shoot occurs • The apical bud inhibits the growth of the axillary buds - therefore the advent of the practice of pruning

8. Modified Stems • Bulb(e.g. onions)when sliced in half, will show concentric rings. • Clove bulblike structures (e.g. garlic) will separate into small pieces when broken apart. • Tuber (e.g. potatoes and daylilies) these structures are either on strings or in clusters underneath the parent plants. • Rhizomeare large creeping rootstock or underground stems and many plants arise from the "eyes" of these roots (e.g. ginger) • Stolons – Horizontal, aboveground stems (e.g. Strawberries) • Cormare similar to bulbs but are solid when cut rather than possessing rings. • Crown(e.g. the type of root structure found on plants such as asparagus) looks much like a mop head under the soil's surface.

9. Bulb

10. TUBERS • A tuber is a solid, enlarged, horizontal, shortened stem; it's a storage area for reserve food. Note in the center of the picture the production of young tubers arising from the rhizome. On the tubers, the so-called "eyes" are the nodes, where new shoots arise at the axil of a scale (modified leaf); these new shoots can give rise to new plants.

11. Rhizomes Ginger, bamboo, many self-naturalizing perennials like lily of the valley

12. Clove Bulblike structures (e.g. garlic) will separate into small segments when broken apart.

13. Corms Solid bulb, without concentric segments

14. Stolons

16. Purpose of roots • The entire root structure serves to anchor the plant/tree in the soil • Absorption of water and nutrients from the soil actually occurs only at the tips of each root fiber • Millions of tiny roots hairs in these tip areas help absorption by increasing surface area

17. Fibrous vs. Tap Roots • Seedless vascular plants (ferns) and Moncot angiosperms such as grasses have fibrous roots • Dicot angiosperm have tap roots

18. Adventitious Roots Roots that grow out of the stem or trunk - sometimes for extra support, sometimes for vegetative reproduction

19. Other modified roots • Aerating roots (or pneumatophores): roots rising above the ground, have a large number pores for exchange of gases. • Buttress roots are large roots on all sides of a tall or shallowly rooted tree. Typically they are found in rainforests where soils are poor so roots don't go deep. They prevent the tree from falling over and help gather more nutrients.

20. More modified roots • Storage Roots: Beets, radish, turnip, horseradish, sweet potato, and cassava (tapioca).

21. Types of leaves Single and double compound leaves Compound Leaves Simple Leaves

22. Modified leaves • Spines on cacti are actually leaves. The photosynthesis is carried out by the green stems • Bracts on poinsettias are actually not petals, but leaves around the tiny yellow flowers Tendrils for grasping

23. LEAF STRUCTURE When guard cells take up water, they become turgid and this closes the stomata. Loss of water from the cells makes them flaccid and this opens the stomata.

24. In a C3 leaf the palisade mesophyll cells typically form a layer in the upper part of the leaf; the corresponding mesophyll cells in a C4 leaf are usually arranged in a ring around the bundle sheath cells. The bundle-sheath cells of C4 plants have chloroplasts (dark green), those of C3 leaves usually lack them. C3 Leaf C4 Leaf Bundle sheath cells surround vascular bundles – thus the name.

25. Review of the typical Plant Cell

26. The Protoplast – the functional, living part of a cell • All areas of a plant cell except the cell wall are considered the protoplast • Cell membrane • Cytosol, • All organelles

27. Major Plant Cells • Parenchyma cells • Collenchyma cells • Sclerenchyma cells • Fibers • Schlereids • Water-conducting cells of the Xylem • Tracheids • Vessel elements • Food-conducting cells of the Phloem • Sieve-tube members • Companion cells

28. Parenchyma cells • Typical plant cell – most abundant in plants • Thin walled (Walls contain cellulose, not lignin) • Unspecialized – can either photosynthesize, or store starch • Can be found in leaves – contain chloroplasts and carry out photosynthesis (mesophyll cells are an example) • Can also be found in roots and other non-photosynthesizing parts and store starch in amyloplasts (related to chloroplasts) – in stems they are called the pith amyloplasts chloroplasts

29. Collenchyma cells • These cells are usually just under the epidermis of leaves, stems and roots • Collenchyma cells are collectively also called the cortex • Cells are columnar in shape • Also lack lignin in their cell walls, but have thicker walls than parenchyma cells • Give younger plants or plant parts support Because they have thick walls but lack lignin, they are able to provide support without restricting growth – hence found in young, growing parts Parenchyma Collenchyma Columnar Collenchyma Epidermis

30. Parenchyma vs. Collenchyma cells

31. Sclerenchyma cells • Thick walls that are fortified with lignin (secondary wall) making them much more rigid than collenchyma walls • Mature sclerenchyma cells usually do not contain protoplasts and cannot grow/elongate, so these cells are located in regions of the plant that have stopped growing

32. Sclerenchyma cont’d. • Two types of sclerenchyma cells: • Fibers - long and thin, exist in bundles in stems, right above above vascular tissue • Sclereids – shorter than fibers and give nutshells and seed coats their hardness. The gritty texture of certain fruit like pears is basically due to sclereids scattered among the parenchyma tissue

33. Xylem Cells • Water conducting • Elongated • Produce lignin-containing secondary walls • Lack protoplasts after maturity • Two types: • Tracheids – spindle-shape, with hole (pits) in them through which water passes • Vessel element cells are broader and lie end to end and form continuous hollow tubes for water to flow through

34. Phloem Cells • Food conducting – sugar, minerals and other organic compounds • Unlike xylem cells, phloem cells can contain protoplasts* (either complete or incomplete) • Two types: • Sieve-tube members – chains of cells that conduct food (partial protoplasts -lack nuclei and ribosomes) • Companion cells – connected to sieve-tube cells, contain nuclei and ribosomes, so help maintain sieve-tube cells *see slide #31 for non-protoplast-containing phloem

35. Sieve-tube elements and companion cells of the Phloem

36. Three Tissue System • The cells we have learned about in the past slides such as parenchyma, sieve tube cells, etc. can be placed into 3 main tissue categories or systems: • Dermal tissue system • Vascular tissue system • Ground tissue system

37. Three Tissue System, cont’d.

38. Cross Section of a Monocot Stem

39. CROSS SECTION OF AN HERBACEOUS DICOT STEM  Epidermis  Collenchyma (also called the cortex – which is ground tissue between the epidermis and the vascular bundles) Sclerenchyma Phloem Vascular bundle Xylem A thin layer of cells called the vascular cambium separates the xylem and phloem  Parenchyma or pith Also known as the Pith in stems – stores food (amyloplasts) and water (central vacuoles)

40. Summary of dicot & monocot stems (Parenchyma) (Collenchyma)

42. Vascular bundles in celery

43. Summary of Monocot vs. Dicot Stems

44. Root Anatomy Pith – a central core of parenchyma cells that store food – mostly in monocots Stele – a vascular bundle that gives rise to both xylem and phloem Pericycle – the outermost layer of the stele that sprouts the lateral roots Casparian strip – a thin strip or coating that prevents water from seeping between cells

45. Epidermis (Dermal tissue) Xylem (Vascular) Cortex or schlerenchyma (ground tissue) Phloem (Vascular) Endodermis (dermal) Pith (Parenchyma or Ground) Pericycle (Parenchyma or Ground tissue) Stele (Entire central Vascular region) Pericycle (Parenchyma or ground) CROSS SECTION OF A MONOCOT ROOT

46. CROSS SECTION OF A DICOT ROOT Endodermis No pith or parenchyma in dicot roots

47. Summary of monocot & dicot roots

48. Growth in Plants • Animals undergo determinate growth – they stop growing after they reach a certain size. • Plants on the other hand have indeterminate growth – they continue to grow throughout their life.

49. Annual, Biennials, Perennials • Botanically, an annual plant is a plant that usually germinates, flowers and dies in one year. (Impatiens, sunflower, gerbera daisies) • A perennial plant is a plant that lives for more than two years. Perennial plants are divided into two large groups, those that are woody and those that are Herbaceous.(Roses, sage, peonies) • A biennial plant is a flowering plant that takes between twelve and twenty-four months to complete its lifecycle.(Parsley, foxglove, sweet William)

50. How can plants have constant growth? • They can have indeterminate growth because they have perpetual embryonic tissues (like stem cells in animals) • These embryonic tissues are called Meristems or cambiums.